1. Field of the Disclosure
The disclosure relates to a casing for a gas turbine engine and particularly, but not exclusively, to a fan case. Also described is a method of manufacturing such a casing.
2. Description of the Related Art
The fan case of a gas turbine engine defines the outer gas path of the engine. It must also be capable of containing a fan blade in the event of a fan blade-off (FBO).
Metallic fan cases are generally machined from oversized ring rolled forgings. To improve the stiffness/weight ratio of the cases, stiffening ribs can be added to the outside of the casing, allowing the barrel wall thickness to be reduced.
Such metallic fan cases generally are seen as having a poor Buy-to-Fly ratio (the weight ratio between the raw material used for a component and the weight of the component itself). The addition of external stiffeners/ribs to reduce the casing weight has a negative impact on the forging input weight which generally makes the Buy-to-Fly ratio of the forging even worse.
Forming the case using a ring rolled forging is also extremely laborious, typically taking over a year to procure and machine ready for dressing.